The issue is whether the Prometheus diagnostic method claims are patent-eligible subject matter under 35 U.S.C. § 101. Those claims are drawn to a method of optimizing suitable dosage ranges of thiopurine drugs to treat an immune-mediated gastrointestinal disorder. There was nothing new about the thiopurine drugs themselves or their use to treat gastrointestinal or autoimmune diseases. The invention was, instead, directed to the method of adjusting the dosage based on levels of patient metabolite levels (as would be determined in a blood test).

Prometheus follows the high profile case of Bilski v. Kappos, which addressed statutory subject matter in the context of business method patent claims for hedging risks in commodities trading. More than 25 amicus briefs were filed in the Prometheus Supreme Court appeal from a broad spectrum of life sciences companies, other high-tech companies, public interest groups and associations of physicians, researchers, medical educators, intellectual property attorneys and the biotech industry.

Before the Federal Circuit, the issue was framed as whether the asserted claims were drawn to a natural phenomenon (not patent eligible) or to a particular application of that phenomenon (patent eligible). The Federal Circuit found the Prometheus claims were directed to the latter.

The Supreme Court argument also highlighted the issue of whether the Prometheus patent claims preempt the use of a law of nature. Mayo argued that the patent claims “monopolize the field of blood testing for thiopurine metabolites, covering anything a physician might do with knowledge of the natural correlation between metabolite levels and health.”

The court questioned whether there was a test by which the courts could determine what is a patentable application of a law of nature and an unpatentable law of nature. What has to be added to a law of nature to make it a patentable process?

The mere scope of the claims also appeared to be bothersome to the court. The justices questioned the extent to which Prometheus’ patent foreclosed competitors. Mayo argued that the sweeping patent claims in this case chill medical research and increase health care costs. Prometheus criticized that position as imposing an analysis of whether a claimed invention hindered or promoted medical research, which would create unpredictable case-by-case results.

Prometheus also sought to justify its claim scope by pointing to other patents that claim a method of gathering information, e.g., for identifying ore deposits or navigating boats in fog.

Another issue was whether 35 U.S.C. § 101 was the right way to review this case—is it more efficient to rely on Section 101 as a threshold patentability question instead of obviousness or novelty to reject invalid patents?

Additionally, although there were references to Bilski, there was no mention of the “machine or transformation” test that was analyzed there and is often the focus in business method cases.